distro: add tests for PodmanDefaultNetBackend

Verify the podman default network backend behavior at multiple levels:
- YAML loading: fake distro YAML with podman_default_net_backend loads
  correctly into ImageConfig
- osCustomizations: the backend file is generated only when both
  containers are present and the option is set
- Real distro cross-check: RHEL 9 has it set to netavark, while
  Fedora and RHEL 10 leave it unset

Signed-off-by: Tomáš Hozza <thozza@redhat.com>

Author: thozza

pkg/distro/defs/loader_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/osbuild/images/internal/common"
 	"github.com/osbuild/images/pkg/arch"
+	"github.com/osbuild/images/pkg/container"
 	"github.com/osbuild/images/pkg/customizations/oscap"
 	"github.com/osbuild/images/pkg/customizations/users"
 	"github.com/osbuild/images/pkg/datasizes"
@@ -702,6 +703,76 @@ image_types:
 	})
 }
 
+func TestDefsDistroImageConfigPodmanDefaultNetBackend(t *testing.T) {
+	netavark := container.NetworkBackendNetavark
+
+	fakeImageTypeYaml := `
+image_types:
+  test_type:
+    filename: foo
+`
+	tests := []struct {
+		name       string
+		distroYaml string
+		expected   *container.NetworkBackend
+		nilImgCfg  bool
+	}{
+		{
+			name: "podman_default_net_backend is loaded",
+			distroYaml: `
+distros:
+  - name: test-distro-1
+    vendor: test-vendor
+    defs_path: test-distro-1/
+    image_config:
+      default:
+        podman_default_net_backend: "netavark"
+`,
+			expected: &netavark,
+		},
+		{
+			name: "podman_default_net_backend absent is nil",
+			distroYaml: `
+distros:
+  - name: test-distro-1
+    vendor: test-vendor
+    defs_path: test-distro-1/
+    image_config:
+      default:
+        locale: "C.UTF-8"
+`,
+			expected: nil,
+		},
+		{
+			name: "no image_config at all",
+			distroYaml: `
+distros:
+  - name: test-distro-1
+    vendor: test-vendor
+    defs_path: test-distro-1/
+`,
+			nilImgCfg: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			baseDir := makeFakeDistrosYAML(t, tt.distroYaml, fakeImageTypeYaml)
+			restore := defs.MockDataFS(baseDir)
+			t.Cleanup(restore)
+
+			dist, err := defs.NewDistroYAML("test-distro-1")
+			require.NoError(t, err)
+			if tt.nilImgCfg {
+				assert.Nil(t, dist.ImageConfig())
+			} else {
+				require.NotNil(t, dist.ImageConfig())
+				assert.Equal(t, tt.expected, dist.ImageConfig().PodmanDefaultNetBackend)
+			}
+		})
+	}
+}
+
 func TestDefsPartitionTableErrorsNotForImageType(t *testing.T) {
 	badDistroYamlMissingPartitionTable := `
 image_types:

pkg/distro/generic/fedora_test.go

@@ -775,3 +775,18 @@ func TestFedoraDistroBootstrapRef(t *testing.T) {
 		}
 	}
 }
+
+func TestFedora_PodmanDefaultNetBackendIsNil(t *testing.T) {
+	for _, d := range fedoraFamilyDistros {
+		t.Run(d.Name(), func(t *testing.T) {
+			a, err := d.GetArch("x86_64")
+			require.NoError(t, err)
+
+			it, err := a.GetImageType("qcow2")
+			require.NoError(t, err)
+
+			cfg := it.(*generic.ImageType).GetDefaultImageConfig()
+			assert.Nil(t, cfg.PodmanDefaultNetBackend, "Fedora should not set PodmanDefaultNetBackend")
+		})
+	}
+}

pkg/distro/generic/images_test.go

@@ -10,8 +10,10 @@ import (
 	"github.com/osbuild/blueprint/pkg/blueprint"
 	"github.com/osbuild/images/internal/common"
 	"github.com/osbuild/images/pkg/arch"
+	"github.com/osbuild/images/pkg/container"
 	"github.com/osbuild/images/pkg/distro"
 	"github.com/osbuild/images/pkg/distro/defs"
+	"github.com/osbuild/images/pkg/rpmmd"
 )
 
 func isoTestImageType() *imageType {
@@ -134,3 +136,118 @@ func TestReplaceBasictemplate(t *testing.T) {
 		assert.Equal(t, replaceBasicTemplate(tc.input, tc.arch), tc.expected)
 	}
 }
+
+func diskTestImageType() *imageType {
+	return &imageType{
+		arch: &architecture{
+			distro: &distribution{},
+		},
+		ImageTypeYAML: defs.ImageTypeYAML{},
+	}
+}
+
+func ostreeTestImageType() *imageType {
+	it := diskTestImageType()
+	it.ImageTypeYAML.OSTree.Ref = "rhel/9/x86_64/edge"
+	return it
+}
+
+func TestOSCustomizationsPodmanDefaultNetBackend(t *testing.T) {
+	netavark := container.NetworkBackendNetavark
+
+	tests := []struct {
+		name         string
+		imageType    func() *imageType
+		backend      *container.NetworkBackend
+		containers   []container.SourceSpec
+		expectFile   bool
+		expectedPath string
+		expectedVal  string
+	}{
+		{
+			name:      "disk: backend set with containers creates file",
+			imageType: diskTestImageType,
+			backend:   &netavark,
+			containers: []container.SourceSpec{
+				{Source: "registry.example.com/test:latest"},
+			},
+			expectFile:   true,
+			expectedPath: "/var/lib/containers/storage/defaultNetworkBackend",
+			expectedVal:  "netavark",
+		},
+		{
+			name:      "disk: nil backend with containers does not create file",
+			imageType: diskTestImageType,
+			backend:   nil,
+			containers: []container.SourceSpec{
+				{Source: "registry.example.com/test:latest"},
+			},
+			expectFile: false,
+		},
+		{
+			name:       "disk: backend set without containers does not create file",
+			imageType:  diskTestImageType,
+			backend:    &netavark,
+			containers: nil,
+			expectFile: false,
+		},
+		{
+			name:       "disk: nil backend without containers does not create file",
+			imageType:  diskTestImageType,
+			backend:    nil,
+			containers: nil,
+			expectFile: false,
+		},
+		{
+			name:      "ostree: backend set with containers creates file in relocated path",
+			imageType: ostreeTestImageType,
+			backend:   &netavark,
+			containers: []container.SourceSpec{
+				{Source: "registry.example.com/test:latest"},
+			},
+			expectFile:   true,
+			expectedPath: "/usr/share/containers/storage/defaultNetworkBackend",
+			expectedVal:  "netavark",
+		},
+		{
+			name:      "ostree: nil backend with containers does not create file",
+			imageType: ostreeTestImageType,
+			backend:   nil,
+			containers: []container.SourceSpec{
+				{Source: "registry.example.com/test:latest"},
+			},
+			expectFile: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			it := tt.imageType()
+			it.ImageConfigYAML.ImageConfig = &distro.ImageConfig{
+				PodmanDefaultNetBackend: tt.backend,
+			}
+
+			bp := &blueprint.Blueprint{}
+			osc, err := osCustomizations(it, rpmmd.PackageSet{}, distro.ImageOptions{}, tt.containers, bp)
+			require.NoError(t, err)
+
+			if !tt.expectFile {
+				for _, f := range osc.Files {
+					assert.NotContains(t, f.Path(), "defaultNetworkBackend",
+						"unexpected defaultNetworkBackend file found at %s", f.Path())
+				}
+				return
+			}
+
+			var found bool
+			for _, f := range osc.Files {
+				if f.Path() == tt.expectedPath {
+					found = true
+					assert.Equal(t, []byte(tt.expectedVal), f.Data())
+					break
+				}
+			}
+			assert.True(t, found, "expected file at %s", tt.expectedPath)
+		})
+	}
+}

pkg/distro/generic/rhel10_test.go

@@ -401,3 +401,18 @@ func TestRH10Rhel10_KernelOption_NoIfnames(t *testing.T) {
 		}
 	}
 }
+
+func TestRhel10_PodmanDefaultNetBackendIsNil(t *testing.T) {
+	for _, fd := range rhel10FamilyDistros {
+		t.Run(fd.name, func(t *testing.T) {
+			a, err := fd.distro.GetArch("x86_64")
+			require.NoError(t, err)
+
+			it, err := a.GetImageType("qcow2")
+			require.NoError(t, err)
+
+			cfg := it.(*generic.ImageType).GetDefaultImageConfig()
+			assert.Nil(t, cfg.PodmanDefaultNetBackend, "RHEL 10 should not set PodmanDefaultNetBackend")
+		})
+	}
+}

pkg/distro/generic/rhel9_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/osbuild/blueprint/pkg/blueprint"
 	"github.com/osbuild/images/pkg/arch"
+	"github.com/osbuild/images/pkg/container"
 	"github.com/osbuild/images/pkg/distro"
 	"github.com/osbuild/images/pkg/distro/distro_test_common"
 	"github.com/osbuild/images/pkg/distro/generic"
@@ -667,3 +668,18 @@ func TestRhel9_DistroFactory(t *testing.T) {
 		})
 	}
 }
+
+func TestRhel9_PodmanDefaultNetBackendIsSet(t *testing.T) {
+	d := generic.DistroFactory("rhel-94")
+	require.NotNil(t, d)
+
+	a, err := d.GetArch("x86_64")
+	require.NoError(t, err)
+
+	it, err := a.GetImageType("qcow2")
+	require.NoError(t, err)
+
+	cfg := it.(*generic.ImageType).GetDefaultImageConfig()
+	require.NotNil(t, cfg.PodmanDefaultNetBackend, "RHEL 9 should set PodmanDefaultNetBackend to work around the cni fallback")
+	assert.Equal(t, container.NetworkBackendNetavark, *cfg.PodmanDefaultNetBackend)
+}